Physical Sciences Division Research Highlights

The Curious World of Water and Ions

The success or failure of solar cells, fuel cells and other alternative forms of energy relies on understanding interactions between ions and water. Researchers such as Dr. Richard Saykally and his colleagues at the University of California, Berkeley are applying new techniques to learn more about these interactions. Saykally recently spoke to scientists at the Pacific Northwest National Laboratory's Frontiers in Chemical Physics & Analysis Seminar Series. The series features academic, government, and industrial leaders who discuss novel ideas and advancements in science.

"Having Richard here was both informative and entertaining," said Dr. Wayne Hess, leader of PNNL's Chemical Physics & Analysis Group and organizer of the seminar series. In his talk, Saykally discussed Hofmeister effects and the ionization of water.

Handling Hofmeister. In the early 1900s, Franz Hofmeister observed that different ions have different strengths in their interactions (e.g., unfolding) with proteins. With careful study and observation, he ranked these strengths, creating the now infamous Hofmeister series, and this same ranking is observed for many different phenomena. The series is infamous because the mechanism behind it is unknown.

Saykally and his team are working to determine the mechanism behind the series. While some theories point to polarizability and ion size, Saykally and his colleagues used femtosecond laser spectroscopy to examine water molecules around simple ions. Based on the experiments, the team believes that the Hofmeister series can be explained by short-range perturbations of the waters of hydration as the ions approach an interface.

Turning Water into Lightning? In studying the Hofmeister series, the team used jets of water that emitted only a few molecules of water. Using these jets led to additional experiments when the team inadvertently turned a jet of water into a bolt of lightning. They found that when water comes through a nozzle, the liquid contains more positive ions (H3O+) than negative ones (OH-) because the OH- attaches to the metal of the nozzle, while the positive ions come through. "You can get enough charge separation to create lightning bolts, which was unfortunate for some of our experiments!" said Saykally.

About Dr. Saykally: Dr. Saykally is a chemistry professor at the University of California, Berkeley. His research focuses on laser spectroscopy of liquids, surfaces, and clusters. Recipient of the Berkeley Distinguished Teaching Award, he has advised 57 Ph.D. and 7 M.S. students as well as 39 post-doctoral fellows. He is co-author of more than 360 scientific articles and recipient of many awards and honors.